U.S. patent application number 11/970137 was filed with the patent office on 2009-04-30 for solar thermal energy collector.
Invention is credited to Randy C. Gee, Roland Winston.
Application Number | 20090107489 11/970137 |
Document ID | / |
Family ID | 40581258 |
Filed Date | 2009-04-30 |
United States Patent
Application |
20090107489 |
Kind Code |
A1 |
Gee; Randy C. ; et
al. |
April 30, 2009 |
SOLAR THERMAL ENERGY COLLECTOR
Abstract
A solar thermal energy collector includes a receptacle and a
tube. The tube is adapted to fit within the receptacle and defines
a first region within the tube and a second region between the tube
and an internal surface of the receptacle. A fluid is circulated
between the first region and the second region for transferring of
the solar thermal energy.
Inventors: |
Gee; Randy C.; (Arvada,
CO) ; Winston; Roland; (Merced, CA) |
Correspondence
Address: |
FOLEY & LARDNER LLP
P.O. BOX 80278
SAN DIEGO
CA
92138-0278
US
|
Family ID: |
40581258 |
Appl. No.: |
11/970137 |
Filed: |
January 7, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61007896 |
Oct 29, 2007 |
|
|
|
60989772 |
Nov 21, 2007 |
|
|
|
Current U.S.
Class: |
126/646 ;
126/651; 126/684 |
Current CPC
Class: |
F24S 10/25 20180501;
F24S 23/74 20180501; F24S 10/45 20180501; Y02E 10/44 20130101; Y02E
10/40 20130101; F24S 10/70 20180501 |
Class at
Publication: |
126/646 ;
126/651; 126/684 |
International
Class: |
F24J 2/12 20060101
F24J002/12; F24J 2/24 20060101 F24J002/24; F24J 2/38 20060101
F24J002/38 |
Claims
1. A solar thermal energy collector, comprising: a receptacle; and
a tube adapted to fit within the receptacle, the tube defining a
first region within an internal surface of the tube and a second
region between an external surface of the tube and an internal
surface of the receptacle, wherein a fluid is circulated through
the first region and the second region for transferring of the
solar thermal energy.
2. The collector of claim 1, wherein the fluid for transfer of
solar thermal energy is mineral oil.
3. The collector of claim 1, wherein the tube is coupled to a
manifold and the manifold is coupled to a pump that circulates the
fluid through the manifold, the first region and the second
region.
4. The collector of claim 3, wherein the manifold is coupled to the
receptacle with a seal.
5. The collector of claim 3, wherein the manifold includes a
tube-in-tube configuration.
6. The collector of claim 3, wherein the manifold is coupled to
additional tubes.
7. The collector of claim 1, wherein the tube is an integral part
of a manifold.
8. The collector of claim 1, wherein the fluid circulates first
through the first region and then through the second region.
9. The collector of claim 1, wherein the receptacle is a dewar, the
dewar having an outer wall and an inner wall, the dewar having a
vacuum drawn between the outer wall and the inner wall, and wherein
the dewar is all glass.
10. The collector of claim 9, wherein the dewar has a thermal
absorption coating on an outer surface of the inner wall.
11. The collector of claim 10 wherein the coating is aluminum
nitride cermets.
12. The collector of claim 1, wherein absent a solar tracker
component and in combination with an external reflector component,
the fluid has a temperature above 280 degrees Fahrenheit when the
fluid exits the receptacle.
13. The collector of claim 1, further comprising an external
reflector for reflecting sun rays onto the receptacle.
14. The solar collector of claim 13, wherein the external reflector
is a compound parabolic concentrator (CPC).
15. A method for collecting solar thermal energy, comprising:
positioning one or more reflectors external to one or more
receptacles, the reflectors being adapted to direct solar thermal
energy to the one or more receptacles; positioning a manifold
having one or more tubes adapted to fit within the one or more
receptacles, each tube defining a first region within the tube and
a second region between the tube and an internal surface of the
receptacle; and circulating a fluid between the first region and
the second region for transferring of the solar thermal energy.
16. The method for collecting solar thermal energy of claim 15,
wherein the fluid is mineral oil.
17. The method for collecting solar thermal energy of claim 15,
wherein the receptacle is a dewar, the dewar has an outer wall and
an inner wall, the dewar has a vacuum drawn between the outer wall
and the inner wall, and the dewar is all glass.
18. The collector of claim 17, wherein the dewar has a thermal
absorption coating on an outer surface of the inner wall.
19. A solar collector for heating a thermal transfer fluid,
comprising: a dewar having an inner wall with an inner surface and
an outer surface, the dewar having an outer wall with an inner
surface and an outer surface, the dewar having a vacuum drawn
between the outer wall inner surface and the inner wall outer
surface, and the dewar having an absorbing material coating the
inner wall outer surface; a fluid tube disposed inside the dewar,
the fluid tube having an inner surface and an outer surface
defining a first region; and a second region disposed in
substantially the complete area between the fluid tube outside
surface and the dewar inner surface of the inner wall; wherein the
thermal transfer fluid flows through both the first region and the
second region.
20. The solar collector of claim 19 further comprising an external
reflector for reflecting sun rays onto the absorbing material
inside the dewar.
21. The solar collector of claim 19, wherein the fluid is mineral
oil.
22. The collector of claim 19, further comprising a manifold
coupled to the receptacle with a seal.
23. The collector of claim 19, wherein the tube is coupled to a
manifold and the manifold is coupled to a pump that circulates the
fluid through the manifold and the first region and the second
region.
24. The collector of claim 19, wherein the tube is an integral part
of a manifold.
25. The collector of claim 19, wherein the manifold is coupled to
multiple tubes.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application claims priority under 35 U.S.C.
.sctn.119(e) from U.S. Provisional Application Ser. Nos.
61/007,896, filed Oct. 29, 2007, and 60/989,772, filed Nov. 21,
2007, incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to the field of
solar thermal energy. In particular, the present invention relates
to solar thermal energy collectors.
[0003] Solar thermal collectors have been utilized for over 20
years. The designs have varied from flat plate, box, air, integral,
unglazed more commonly to parabolic troughs and dishes and full
power towers. Though they have been commercially available for over
20 years, recent designs of evacuated tubes have become more
efficient and less costly, allowing them to be both commercially
and domestically available as well as more widely utilized. Some
devices contain heat removal inserts that are placed within the
tubes that serve the purpose of transferring the collected energy
to a heat-transfer fluid, which is circulated to a manifold located
at the end of the tubes or in connection with the inserts.
[0004] Conventional designs are limited in their ability to
transfer heat from the collector. It is desirable to improve the
efficiency with which such heat is transferred to the heat-transfer
fluid.
SUMMARY OF THE INVENTION
[0005] In one aspect, the invention includes a solar thermal energy
collector comprising a receptacle and a tube. The tube is adapted
to fit within the receptacle and defines a first region within an
internal surface of the tube and a second region between an
external surface of the tube and an internal surface of the
receptacle. A fluid is circulated through the first region and the
second region for transferring of the solar thermal energy.
[0006] In one embodiment, the fluid for transfer of solar thermal
energy is mineral oil.
[0007] In one embodiment, the tube is coupled to a manifold, and
the manifold is coupled to a pump that circulates the fluid through
the manifold, the first region and the second region. The manifold
may be coupled to the receptacle with a seal. The manifold may
include a tube-in-tube configuration. The manifold may be coupled
to additional tubes.
[0008] In one embodiment, the tube is an integral part of a
manifold.
[0009] In one embodiment, the fluid circulates first through the
first region and then through the second region.
[0010] In one embodiment, the receptacle is a dewar, the dewar
having an outer wall and an inner wall, the dewar having a vacuum
drawn between the outer wall and the inner wall, and wherein the
dewar is all glass. The dewar may have a solar-radiation absorption
coating on an outer surface of the inner wall. The coating may be
aluminum nitride cermets.
[0011] In one embodiment, absent a solar tracker component and in
combination with an external reflector component, the fluid has a
temperature above 280 degrees Fahrenheit when the fluid exits the
receptacle.
[0012] In one embodiment, the collector further comprises an
external reflector for reflecting sun rays onto the receptacle. The
external reflector may be a compound parabolic concentrator
(CPC).
[0013] In another aspect of the invention, a method for collecting
solar thermal energy includes positioning one or more reflectors
external to one or more receptacles, the reflectors being adapted
to direct solar thermal energy to the one or more receptacles;
positioning a manifold having one or more tubes adapted to fit
within the one or more receptacles, each tube defining a first
region within the tube and a second region between the tube and an
internal surface of the receptacle; and circulating a fluid between
the first region and the second region for transferring of the
solar thermal energy.
[0014] In another aspect, the invention includes a solar collector
for heating a thermal transfer fluid. The collector comprises a
dewar having an inner wall with an inner surface and an outer
surface, the dewar having an outer wall with an inner surface and
an outer surface, the dewar having a vacuum drawn between the outer
wall inner surface and the inner wall outer surface, and the dewar
having an absorbing material coating the inner wall outer surface;
a fluid tube disposed inside the dewar, the fluid tube having an
inner surface and an outer surface defining a first region; and a
second region disposed in substantially the complete area between
the fluid tube outside surface and the dewar inner surface of the
inner wall. The thermal transfer fluid flows through both the first
region and the second region.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 illustrates a solar thermal energy collector
according to an embodiment of the present invention;
[0016] FIGS. 2A and 2B illustrate cross-sectional views taken along
II-II of FIG. 1 of solar thermal energy collectors according to
embodiments of the present invention; and
[0017] FIG. 3 illustrates a cross-sectional view taken along
III-III of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] Embodiments of the present invention provide devices,
methods and systems for collection and/or transferring of solar
thermal energy. In this regard, embodiments of the present
invention may provide inexpensive and efficient manners for
collection of solar thermal energy.
[0019] Referring to FIGS. 1, 2A and 2B, a solar thermal energy
collector according to an embodiment of the present invention is
illustrated. In the illustrated embodiment, a collector 100
includes one or more receptacles 120 coupled to a manifold 110. The
manifold 110 includes an inlet pipe 112 and an outlet pipe 114 for
circulating fluid through the manifold 110 and the collector 100. A
pump 116 is optionally provided to circulate the fluid 110. The
dimensions of the inlet pipe 112, the outlet pipe 114 and the pump
116 may be selected according to the requirements of the specific
implementation of the collector 100.
[0020] The manifold 110 is coupled to one or more receptacles 120.
The number of receptacles 120 may be selected from any practical
number dependant on the size of the collector system desired.
Further, the manifold may be coupled to a plurality of receptacles
in a serial manner, a parallel manner or any combination thereof. A
seal 118 is provided to prevent leakage of the fluid from the
manifold 110. In one embodiment, the seal 118 includes O-ring
compression seals. In other embodiments, other types of seals may
be used. Preferably, the seals allow simple and efficient assembly
of the manifold 110 and the receptacle 120 while ensuring
prevention of leakage.
[0021] Each receptacle 120 is preferably an all-glass dewar having
a double-wall configuration, as most clearly illustrated in FIGS.
2A and 2B. Of course, in other embodiments, various other types of
receptacles may be used. In one embodiment, the receptacles are
cylindrical borosilicate glass bottles with a closed end, as
exemplarily illustrated in FIG. 1. Each dewar 120 is provided with
an inner wall 122 and an outer wall 124. The region between the
inner wall 122 and the outer wall 124 is evacuated. The vacuum
region results in low heat loss. The level of evacuation of the
region between the inner wall 122 and the outer wall 124 may be
varied to either increase efficiency (e.g., reduce heat loss) or
improve cost-effectiveness.
[0022] In one embodiment, an outer surface of the inner wall (i.e.,
the surface facing the vacuum region) is coated with a
solar-radiation absorption coating 126, such as aluminum nitride
cermets. In other embodiments, other commercially available
coatings may be used. The solar-radiation absorption coating 126
facilitates absorption of solar thermal energy by the receptacle
120.
[0023] Each receptacle 120 is provided with a tube 130 adapted to
fit within the receptacle 120. In one embodiment, on one end, the
tube 130 is inserted into the receptacle 120 and has an open end.
As illustrated in FIG. 1, the open end of the tube 130 is spaced
apart from the end of the receptacle 120. The amount of space
between the open end and the end of the receptacle 120 is
sufficient to allow fluid to flow freely around the open end of the
tube 130. On the other end, the tube 130 is coupled to the manifold
110, which is coupled to a tube corresponding to each of the other
receptacles of the collector 100. The tube 130 may be coupled to
the manifold 110 in a variety of manners including, but not limited
to, welding. In one embodiment, the coupling of the manifold 110
and the tube 130 includes used of screw-type threads formed on
manifold 110 and the tube 130, similar to those found on
conventional plumbing joints, that may use a thread seal. In a
particular embodiment, as illustrated in FIGS. 1, 2A and 2B, the
tube 130 is an integral part of the manifold 110. In this regard,
the tube 130 may be formed as an integral part of the manifold and
does not include any joints, connections or seals. Thus, once
created, the tube 130 may not easily be removed from the manifold
110. The integral configuration of the tube 130 and the manifold
110 reduces the number of parts required, thereby reducing the time
and effort required for installation and assembly of the collector
100 in the field. Thus, during assembly, the receptacle 120 only
needs to be positioned around the tube 130 and secured with, for
example, the seal 118. Further, the integral configuration
eliminates a potential leakage point for fluid flowing through the
receptacle, as described below.
[0024] In accordance with embodiments of the present invention,
assembly and maintenance of the collection 100 is simplified. With
the tube 130 integrally formed (or otherwise pre-assembled) with
the manifold 110, only the receptacle 120 needs to be connected.
Thus, for maintenance purposes, individual receptacles that may
become damaged can be replaced without replacing the entire
collector 100. Further, use of appropriate seals 118 between the
receptacle 120 and the manifold 110 can make such replacement of
receptacles simple, time-efficient and effective. A worker in the
field can accomplish such maintenance without expending substantial
time and effort.
[0025] The receptacle 120 and the manifold 110 are positioned such
that an external reflector 140 concentrates solar thermal energy
(or solar irradiance) onto the receptacle 120. The shape of the
reflector 140 may be selected from a variety of shapes. In some
embodiments, the reflector 140 may operate in conjunction with a
solar tracking component. Preferably, the reflector 140 is adapted
to operate in the absence of such a tracking component. In one
embodiment, the external reflector 140 is a compound parabolic
concentrator (CPC). Such reflectors are well known to those skilled
in the art.
[0026] FIGS. 2A and 2B illustrate two embodiments of an external
reflector 140a, 140b for use with embodiments of the present
invention. Referring first to FIG. 2A, the external reflector 140a
has two concave, parabolic components joined by a central convex,
v-shaped component. Each concave component forms substantially half
of a parabola.
[0027] Referring now to FIG. 2B, the external reflector 140b
includes two concave, parabolic segments joined to each other. In
this embodiment, each concave component forms substantially more
than half of a parabola. In this regard, the two concave segments
join to form an inverted "v" shape.
[0028] Thus, the shape of the reflector 140 directs substantially
all sunlight incident on the reflector 140 within a predetermined
angle of incidence onto the receptacle 120 and, more specifically,
onto the thermal absorption coating 126 on the outer surface of the
inner wall 122 of the dewar 120. In this regard, sunlight is
concentrated efficiently onto the receptacle 120 while minimizing
heat loss. Further, the evacuated, double-wall configuration of the
dewar 120 facilitates minimizing of the heat loss. Thus, sufficient
efficiency of the collector 100 can be achieved in the absence of a
solar tracking component, thereby resulting in significant cost
reduction. The combination of the reflector 140 and the receptacle
120 is preferably configured to have a large acceptance angle. For
example, in one embodiment, an acceptance angle of at least .+-.35
degrees. Thus, sunlight within at least a 70-degree range is
captured, and the associated solar thermal energy is collected.
[0029] To facilitate collection of solar thermal energy, the
reflector 140 may be configured specifically to capture energy
within the solar spectrum. In this regard, the reflector 140 may be
formed of a material optimized for the solar spectrum of energy. In
some embodiments, the reflector 140 may be coated with a material
for such optimization.
[0030] In one embodiment, a protective cover 150 is positioned
above the receptacles 120. The protective cover 150 may be sized to
cover multiple receptacles 120. Alternatively, a single protective
cover 150 may be positioned above each receptacle 120. The
receptacle is preferably formed of a transparent glazing, such as
soda lime glass, which does not interfere with the transmission of
sunlight to the reflectors 140.
[0031] To further prevent such interference, the protective cover
150 may be provided with an anti-reflective coating. Such
anti-reflective coating ensures that sunlight is transmitted to the
reflectors 140 without substantial reflecting of the sunlight away
from the collector 100. The anti-reflective coating may be applied
to either the inner surface of the protective cover 150 (i.e., the
surface facing the reflector 140 and the receptacle 120) or the
outer surface of the protective cover 150. In one embodiment, a
similar anti-reflective coating may also be applied to a surface of
the receptacle 120. The anti-reflective coating may be formed of
any of a variety of materials. In one embodiment, the
anti-reflective coating includes multi-layer, solgel texturing.
Thus, collection of solar thermal energy is permitted while
providing protection of the collector 100 from debris, for
example.
[0032] In operation, a fluid is circulated through the manifold 110
via the pump 116. The flowrate of the fluid through the manifold
110 may be adjusted for particular conditions and particular
implementations. The fluid circulates through the inlet pipe 112
and into the tube 130 within the receptacle 120. In embodiments in
which the tube is integral with the manifold 110 (and the inlet
pipe 112), no leakage issues are present. The positioning of the
tube 130 within the receptacle 120 forms a circulation path within
the receptacle 120. The circulation path includes a first region
132 within an internal surface of the tube 130 and a second region
134 between an outer surface of the tube 130 and an inner surface
of the inner wall 122 of the receptacle 120. Thus, in one
embodiment, the fluid is circulated first from the inlet pipe 112
through the first region and then through the second region. In
this regard, while the fluid is flowing, it occupies substantially
the entire volume within the receptacle 120 with one direction of
flow occupying the volume in the first region and the opposite
direction of flow occupying the second region. The fluid then exits
the receptacle 120 to the outlet pipe 114. The seal 118 prevents
leakage of the fluid as it exits the receptacle 120. Those skilled
in the art will understand that the circulation path (inlet pipe to
first region to second region to outlet pipe) may be reversed in
other embodiments, which are also contemplated within the scope of
the present invention.
[0033] Thus, solar thermal energy is directed by the external
reflector 140 onto the receptacle 120. The solar thermal energy is
absorbed by the receptacle 120 and, more specifically, the
absorption coating 126 on the outer surface of the inner wall 122
of the receptacle 120. As noted above, the evacuated region between
the inner wall 122 and the outer wall 124 facilitates reduction in
heat loss, thereby improving efficiency of the collector 100. While
circulating through the first region 132 and the second region 134,
the fluid is heated, thereby facilitating transfer of solar thermal
energy from the collector 100. Since the fluid flows through the
second region and adjacent the inner wall 122, the thermal energy
is more directly transferred from the absorption coating 126 to the
fluid flowing through the receptacle 120. The fluid then carries
the thermal energy out of the receptacle in the form of heat,
whereby the fluid is heated by the thermal energy as it flows
through the receptacle. The fluid circulated through the collector
100 may be selected from a variety of fluids. In one embodiment,
the fluid is mineral oil.
[0034] Embodiments of the present invention are capable of heating
the fluid to temperatures of above 280 degrees Fahrenheit without
the use of a solar tracker component. Certain embodiments are
capable of heating the fluid to temperatures of above 300 degrees
Fahrenheit as the fluid exits the receptacle 120. Thus, embodiments
of the present invention can provide efficient collection of solar
thermal energy in a cost-effective manner.
[0035] In one embodiment, the fluid is selected such that the
boiling point of the fluid is higher than the maximum temperature
reached by the fluid within the receptacle 120, typically at the
point at which the fluid exits the receptacle 120. In this regard,
the fluid does not boil while circulating within the receptacle 120
and, therefore, does not exert additional pressure on the walls of
the receptacle 120. Accordingly, the receptacle 120 may be formed
of a greater variety of materials. In a particular embodiment, the
avoidance of additional pressure on the walls allows the receptacle
120 to be formed of glass.
[0036] In various embodiments, the fluid is selected such that the
flash point of the fluid is higher than the maximum temperature
reached by the fluid. In this regard, in the event of a leakage of
fluid in the system (e.g., from the manifold in the region of the
seal 118), the fluid does not ignite, thereby presenting a fire
hazard. Accordingly, the system is made inherently fire-safe.
[0037] In one embodiment, the manifold 110 has a tube-in-tube
configuration, as exemplarily illustrated in FIG. 3. In this
regard, the inlet pipe 112 is positioned within the outlet pipe
114. In one embodiment, the inlet pipe 112 and the outlet pipe 114
are concentrically positioned. Such tube-in-tube configuration may
facilitate assembly of the manifold with the receptacles 120. In
alternate embodiments, the inlet pipe 112 and the outlet pipe 114
are separated tubes.
[0038] While particular embodiments of the present invention have
been disclosed, it is to be understood that various different
modifications and combinations are possible and are contemplated
within the true spirit and scope of the appended claims. There is
no intention, therefore, of limitations to the exact abstract and
disclosure herein presented.
* * * * *